If you have a job with paid vacation days, or the means to take a random day off, I really recommend taking a random Wednesday from time to time to just clear the decks and do your art thing all day (or sports thing or whatever you care about more than your job!) I used to hoard my vacation days and only take a full week at a time, but I find a Big Wednesday can do a lot for me, especially in the winter.
Sure, a Friday or Monday are also great, but for me I love knowing I only have two days of slog on either side of that golden Wed!